This disclosure relates to the technical field of computer vision. In computer vision, mathematical techniques are used to detect the presence of and recognize various items that are depicted in digital images. Localized portions of an image, on which specific types of computations are performed to produce visual features, may be used to analyze and classify objects depicted in the image. Low-level features, such as interest points and edges, edge distributions, color distributions, shapes and shape distributions, may be computed from portions of an image and used to detect items that are depicted in the image. Machine learning algorithms can be used for feature recognition.